This invention relates generally to lasers and more particularly to solid state lasers operating in the blue-green spectral region.
Blue-green lasers are very desirable for underwater uses due to their low transmission losses in water. Such lasers include metal vapor lasers, gas lasers and frequency doubled solid state lasers. It has been found that a relatively efficient laser system emitting pulses of short duration in the blue-green spectral region may be constructed by using a dye laser pumped by a mercury capillary lamp to, in turn, pump a Praseodymium doped solid state laser, as described in U.S. Pat. No. 4,052,852 to Nicolai issued Oct. 18, 1977. In this laser system, a good spectral match is achieved between the capillary lamp and the dye laser, providing good power coupling and efficiency. By Q-switching, solid state laser pulses of high power and short duration are produced. Unfortunately, this laser system has been subject to serious limitations because the threshold for lasing using previous methods has been higher than the damage threshold of the laser crystal. Since this is a three level laser, the flexibility and options available for reducing the power requirements for lasing are severely limited.
Deficiencies in other blue-green lasers are low efficiency, reliability, repetition rate, pulse energy, lifetime, and extremely low temperature operation which makes such use impractical. It is desirable to develop a laser around 4800 A which would have performance and reliability specification similar to Nd:YAG at 1.06 .mu.m. Unfortunately, double YAG at 0.53 .mu.m is too long a wavelength for many applications.